Apparatus for heat-treating granular materials



Allg- 29, 1950 J. B. HENwooD 2,520,637

APPARATUS FOR HEAT-TREATING GRANULAR MATERIALS l 3 Sheets-Sheet 1 Filed061'.. l0, 1946 INVENTOR. W )W rra//vfy J. B. HENWOOD Aug. 29, 1950APPARATUS FOR HEAT-TREATING GRANULAR MATERIALS '3 Sheets-Sheet 2 FiledOct. l0, 1946 mf/ :hl: Inutili.; lillnni H., m 5 m INVENTOR.

am MMM BY MMM MHTTF/VEY IN V EN TOR. Wig

5 Sheets--Sheerl 3 l l l J. B. HENWOOD APPARATUS FOR HEAT-TREATINGGRANULAR MATERIALS Aug. 29, 1950 Flled oct 1o, 1946 Alashed Att. 29.1950 1,520,637

ation Anl.' lfitti;flh'il delphia n offrfrehhsylvani t, whish, .gas.passes .with tion iff* press' 'The underside, ofl t .t fluidizlh so t.s ,and r111 a mannnbharderiwd i byfthe" r'alsence ofanyobjectionablejjet e'ie'ct at localized regionsoi thelie'artliLvInf'the' preferred f efhbqdm ntf shwn, 'flacctrhplnish this byyprovi"dl`ng` aplralityoi cells alongside offeachv other directly beneathan elongated sieve-like hearth, Teach' c'ellffbeing' in'funob'strctedcommunication with a portion fofr` tliehearth'i l'hecellsrfat' the .fbottomsfthereof' alrelp'ro'vided Vwitlr'one or more g.pressurerelucingga'sapertures5so thatfanadequate flow rate of gas isobtained through the cellsvitofzfluidizerfthefsolids. ffHow'ever," theaperturesy are iof such :sizeffthat '.th'e .velocity pressure v.ofthegaspassing throughnthfaperturesis substantially converted to staticpressure in"4 the cells, if lyvllereby-` the-gas'hpasses throughout allregions .Lowthe `bed :ofl solids without Vsubjecting the solidsto,-.any2 fundesirable v ietwveectgfon account of the Hbeing prcmoted,by the as "I'tfisalreadv-k h, Y l Y f ativ1y'isma11 in si .insuhdividedfotmfcan l becoriveyedalon Vz'o tallyfdisposedhhearthslthoughfalbed materialin' `fluid- "apertures-Vif". "SP1" ,i f

Th ayeragefdepth fithe bed of solids grady lecxjeascs; frornzfthe inletend to the outlet n end-lof the-hearthlithe portion of the bed directlyabove each cell normally having a denite averr,-xagl; d epth..I,By-providing a plurality ofcells be- Anea tieve-like hearth, anarrangement is videdi whereby the static pressure in any parul`ar.cellwill automatically vary when the of the solids above it tends toincrease or static pressure in the cells can vary over a pres- 3`5"'surerange up to a maximum value substantially corresponding to the staticpressure of the gas at the inlet side of the pressure reducing gasapertures. By maintaining the normal average depth of the bed of solidsat the inlet end of the 40 hearth at a denite maximum value which can beeffectively uidized and aerated, when the becomes unduly static pressureof the gas developed in the cells eof, clogging may at the inlet end ofthe hearth is somewhat less @comes too shallow than the maximum valuejust referred to, the th reof, the solids at such gas in the cells willalways be eiective to -peney'blown away to produce trate the solids atall regions of thehearth to heath through which the gaspromote uuid-likenow of such material When it is desired to heat the solids while beingo' ance 1th my invention, an improveconveyed on the hearth, provision ismade for provided whereby the desiredy thickness producinghightemperature heating gases and '-the"bedof solids is alwaysmaintained on the utilizing such gases to iluidize the solids. In suchmel average, @spilt P thearth, o n'g d di velocity fpressurepeoftheffgasentering the cell` hearth from the inlet end to the outlet endcase, the heat losses from the solids being con-l t f." I accomplishthis by providing a sieveveyed on the hearth is an important consider-*Y like `vperforated hearth upon which the bed of ation and should bekept at a minimum. I acsolids is adapted to be supported and throughcomplish this by providing a hearth having hol- 3 low side wallsextending upwardly therefrom and into which is diverted some of the hightemperature gases passing to the underside of the hearth to fluidize thesolids.

It has already been pointed out above that when heating of the solids isdesired, uniform heating of the material is often an importantconsideration. In order further to insure uniform heating of all of thesolids, the rate at which the solids pass and move over the hearth maybe controlled responsive to a condition influenced by the temperature ofthe heated solids at or adjacent to the region at which the material isdischarged from the hearth.

'I'he novel features which I believe to'be characteristic of myinvention are set forth with particularity in the claims. The invention,both `as to organization and method, together with the objects andadvantages thereof, will be better understood by reference to thefollowing description taken in connection with the accompanyingdrawings, of which:

Fig. 1 is a side vertical sectional view of apparatus embodying theinvention;

Fig. 2 is a transverse vertical sectional view.

` taken at line 2-2 of Fig. 1, to illustrate the invention more clearly;

Fig. 3 is an enlarged fragmentary sectional view similar to Fig. 2, toillustrate details of the invention;

Fig. 4 is a fragmentary horizontal sectional view, taken at line 4-4 ofFig. 2;

Fig. 5 is a fragmentary view in elevation of the discharge end of theapparatus of Figs. l and 2; and

Fig. 6 is a view more or less diagrammatically showing the combustiblefuel supply lines for the apparatus of Figs. 1 and 2 and controlprovisions therefor.

Referring to the drawings, and especially to v Figs. 1 and 2 thereof, I`have shown the invention embodied in apparatus in which subdividedmaterial is conveyed with the aid of a gas. More particularly, theapparatus comprises a `furnace unit I in which a high temperature gas isemployed not only to convey the subdivided. material but also to effectheating thereof while the material is being conveyed.

'Ihe furnace unit I0 comprises a refractory wall structure includingspaced apart side walls I I, end walls I2 and a bottom I4 which aredisposed within an outer metallic shell I which is supported in anelevated position above a foundation I8 by'approprlate framework I1. Inthe space between the side walls `II and extending lengthwise thereof isprovided a perforated elongated ,hearth I8 upon which the subdividedmaterial is supported and along which such material is adapt- 'ed totravel from an inlet I9 to a discharge opening 28.

The inlet I8 is formed by a closed inclined chute .2l which extendsthrough an end wall I2 and terminates at its lower'end at a regionimmediately above one end of the hearth I8. The

upper end of the chute 2l is fixed toa hopper 22 for the subdividedmaterial. trically operable mechanical vibrator 23 of any well knowntype may be ilxed to the upper end of the chute 2I to agitate andvibrate the hopper 22 and chute to prevent clogging and jamming of thesubdivided material andv insure continuous feeding of the material ontothe hearth I8. The discharge opening 20 is formed by an inclined y chute24 which extendsdownwardly from an end 4 of the hearth I8 and passesthrough an opening in the opposite end wall I2,

In the furnace unit I8 being described, heatedl side walls II at theirlower ends.

A suitable elecv As shown in Fig. 6, a combustible fuel mixture may bedelivered to each row of burners 25 from a source of supply through amain conduit 28 and branch conduits 28 and 38 which are connected tomanifolds 3I and 32, respectively. The

combustible fuel mixture passes from the manifolds 3I and 32 throughconduits 33 communieating with the burners 25. Suitable controls,including valves 34 and 35 connected in the conduits'just described, maybe provided to control the pressure and rate at which the combustiblefuelmixture is individually supplied to each burner 25. The burners 25preferably are of a type capable of producing high temperature productsof, combustion. By way of example, the burners 25 may be of the kinddescribed and illustrated in Hess Patent No. 2,215,079, granted onSeptember 17, 1940, and, if desired, reference may be had thereto for adetailed description of the burner structure.

In order to deliver gases over a wide temperature range to the undersideof the hearth, air or any suitable gas is supplied through the slot 26which mixes with the products of combustion produced and developed bythe burners 25. As best shown in Fig. 2, provision is made forrecirculating the spent heated gases and adding fresh air to suchrecirculat'ed gases.

To this end a suitable roof is provided for the furnace unit III. Forreasons which will be given presently, the roof for the furnace unit I8in the instant embodiment includes an insulated portion 36 and anuninsulated portion 31 having the side walls thereof spaced apart thesame distance as the side walls I2 at the opening at the upper endsthereof. 'I'he two roof portions 36 and 31 collectively extend betweenthe end walls I2 of the furnace unit I0. 'I'he spent heated gasespassing into the roof portion 31 may be discharged therefrom through aconduit 38 directly into the atmosphere, while the spent heating gasespassing into the roof portion 3j pass therefrom through a conduit 39into a separator 4I) for separating from gie gases any materialin afinely divided condi- The gases stripped of foreign matter pass from theseparator 40 through a conduit 4I which is connected to the inlet ofablower 42, the outlet end of which is connected by branch conduits 43(only one of which is shown in Fig. 2) for discharging the recirculatedgases into the spaced apart regions of an elongated hollow metallicshell 44. The shell 44 is fixed to the underside of the refractorybottom I4 and is coextensive in length with the slot or passage 26 whichis in communication with the shell. As bestV shown in Fig. 1, the branchconduits 43 are connected to the shell 44 at regions more or lessdirectly beneath the roof portions 36 and 31.

As shown in Fig. 2, the portion of the conduit 4I adjacent to the bendtherein immediately above the separator isf-provided with a damper con-I trolledopening 45 for discharging fspent` gases .1- y from thegasrecirculation system'just described.

A second damper controlled opening 48 is also d provided in the conduit4I for adding make-up. air. The damper controlled openings 45 and 46 maybeof any conventional adjustable typewhichl canbe regulated to adjusttheproportion of the spent gasesdischarged from the gas recirculationsystem and theamount of` make-upvair mixed with the spent gases.

In this way the temperature of the gases'passing through the opening 21from the region of the burners 25 can be adjusted by regulating theproportion of make-up vair added to the recirculated gases whichsubsequently mix with the high temperature products of combustion at theupper end of theslot or opening 26. It is to be understood that thegases mixed with theproducts of combustion may be air or any othersuitable gas, depending upon the composition of the subdivided materialconveyed on the hearth I8 and the nature of the treatment to which thesubdivided material is to be subjected, whether chemical and/or physicalin character.

In certain instances it may be desirable to dispense with gasrecirculation, and, when it is desired to employ especially hightemperature gases to act on the subdivided material on the hearth I8,the heating gases may consist entirely of heated products of combustion.In such case, the products of combustion may either be oxidizing orreducing in character or substantially neutral: by regulating theproportion of fuel and combustion supporting gas in the combustible fuelmixture supplied to the burners 25. as described in Hess Patent No.2,215,080, granted on September 17, 1940.

In accordance with the invention, in order to convey subdivided materialat a uniform rate on the hearth I8 and thus eifect substantially uniformheating of the material Vby the heating gases passing upwardly throughthe opening 21, thel theoutlet end of the heartnlis formed with deadairspaces, as indicatedfat 53 in Fig.j1.

Inthe furnace unit Ill being described, refractory shapes are employedto form the'cells 41 and bottom sections of the hollow walls 50 which,in the' embodiment illustrated," extend below the v hearth I8. 'Therefractoryshapes comprise bot- Each refractory shape is formed with anintegral upstanding wall section which includes spaced apart parallelwalls 55 and a connecting trans- 'verse end wall which serves as apartition 48 extending to the inner surfaces of the side walls I I.Hence, each upstanding wall section of a refractory shape forms threewalls of a cell unit 41, and, when the refractory shapes are assembledsnugly together in abutting relation in the manner shown in Fig. 1, thetransverse end of each upstanding wall section closes off the parallelwalls 55 of an adjacent wall section to form an independent cell unit.

The walls 55 of the refractory shapes are spaced from the inner surfacesof thefurnace side walls II to form the lower sections of the hollowwalls or passages 50. In addition to the apertures 49 perforated hearthI8 is provided with ay multi- Y plicity of openings distributedthroughout all effective regions thereof. Preferably, the hearth I8 issieve-like in character and such that the heated gases pass therethroughwith substantially no reduction in pressure. In the instant embodiment,the sieve-like hearth is obtained by employing screening formed of hightemperature alloy material capable of withstanding the high temperatureheating gases which pass therethrough.

Immediately beneath the elongated hearth I8 a number of small chambersor cells 41 are provided having partitions 48 therebetween which extendtransversely of the hearth. The cells 41 collectively extend from theinlet I9 to the outlet 20 and at the upper ends thereof are inunobstructed `communication with the perforated hearth I8. As seen inFigs. 1, 2 and 4, the bottom of each cell 41 is formed with a numberv ofpressure reducing gas apertures 49. d

In order to effectively heat the subdivided material on the hearthl I8to the desired high temperature by the heating gases and-to reduce heatlosses therefrom to a minimum, the side walls 58 formed therein, thebottom plates of the refractory shapes are formed with openings 56through which a portion of the heated gases is diverted into the lowerends of the hollow walls 50.

The upper thickened ends of the side walls are formed with recesses toreceive the bent sides 51 of the hearth screen. In order to prevent gasleakage at the lateral edges of the hearth screen AI8 and betweenadjacent cells 41, suitable clips 56 y pins 6I, the smaller lowerportions of which t into apertures formed in the outwardly extendingflanges 59 of the refractory shapes.

The hollow refractory tubesy 60 are in abutting relation at each side ofthe hearth I8 and collectively form the upper sections of the hollowside Walls 50 which extend upward from the hearth. The tubes '60 are ofsuch length that they t snugly between the flanges 59 and notchedregions at the upper parts of the sidewalls II, as

indicated at 62 in Figs. 2 and 3. The extreme upper ends of the tubes 60are closed to .provide a suitable bearing surface at the notched regions62 and are formed with openings 63 through which the diverted heatedgases emerge and mix with the heated gases passing vupwardly through thehearth I8 into the space 5I.

The furnace unit I0 is divided into two heating zones by suitablepartitions. As best shown in Fig. 1, a transverse partition 64 extendsdownwardly from the juncture of the roof portions 36 and 31 andterminates at the upper'ends of the hollow tubes 60. A transverserefractorypartition l651s also provided beneath the cells 41 at a regionimmediately below thefpartition 64. The refractory partition 65 islocated between the manifolds 3l and 32 at each side of the furnace 7unit I0. A partition 66 is also provided in the shell 44 which isdirectly beneath the refractory partition 65. The partition 66 isprovided in the shell' 44 in the event it becomes desirable to sup- .plyrecirculated gases only to thek outlet end of the hearth I 8 and tosupply fresh air to the heating zone at the inlet end of the hearth, asby a suitable blower (not shown), for example. i

In order to regulate the temperature of the heating gases supplied tothe two heating zones at opposite sides of the partition 65, a suitablecontrol system is provided including a pair of thermocouple members 61and 68 which extend into the space 52 through a side Wall II, asvshownin Fig. 2. The thermocouples 61 and 68 extend l branch conduits 29 and30 when the temperature of the heating gases in the space 52 tends tofall and rise, respectively, from a predetermined or definite value. l

In order further to insure uniform heating of the subdivided material, asuitable control is provided for regulating the rate at which thematerial is conveyed on the hearth I8. As best vshown in Figs. 1 and 5,this is accomplished in the instant embodiment by providing a verticallymovable gate 12 for the chute 24 which is raised and lowered at thedischarge opening or outlet 20 responsive to a thermocouple member 'I3arranged to extend through the end wall I2 at such a height that theinner end thereof is contacted by the heated subdivided material aboutto pass from the hearth I8into the discharge outlet 20.

As shown in Fig. 5, the gate 12 is connected through a lever system to acontrol member 14 of a diaphragm operated device 15 which is operativelyassociated with any Well known control equipment 16 like that known inthe trade as a valve positioner. is connected in an air supply line 11,and the pressure at which air is supplied thereto is regulated by Janelectromagnetically operable valve 18 of the proportional type. Thevalve 18 is regulated by a suitable electronic control 19 of any wellknown type which is connected by conduits 80 to a source of electricalsupply and to which the thermocouple member 13 is also connected.

It will now be undeirstood that when the temperature of the subdividedmaterial about to pass into the discharge opening 20 tends to changefrom a definite value, the electronic control 19 responds tothermocouple member 13 and causes the Valve 18 to vary the pressure ofthe air supplied to the control equipment 16. The

control equipment 15 responds to such variations in air pressure to movethe control member 14 of the diaphragm operated device 15 which in turnmoves the gate 12 at the discharge opening 20. When the temperature ofthe subdivided material about to pass into the discharge opening 20tends to rise above a definite value, the control system just describedacts to raise the gate 12; and

The control equipment 16v conversely, when the temperature of suchsubdivided material tends to fall from the definite value, the controlsystem acts to lower the gate 12.

In placing the material conveying apparatus just described in operation,solids of relatively small size or in subdivided form are supplied tothe hopper 22 and flow` therefrom by gravity through the chute 2| ontothe hearth I8 at the inlet end thereof. The chute 2| at its lower end isas wide as the distance between the hollow side walls 50. As previouslyexplained, clogging of material in the hopper and inlet chute is avoidedby providing the vibrator 23.

The height or depth of the bed of material on the hearth I8, at theregion thereof adjacent to the inlet opening I 9, is dependent upon theposition of the lower edge of a feed gate 8| which is removably securedat its upper end at 82 to the chute 2|. For different materials anddifferent rates at which it is desired to move the materials on thehearth I8, a feed gate 8| of appropriate size can be selected to givethe desired depth of the bed of material at .the inlet end of thehearth.

The depth of the bed of material on the hearth I8 at the outlet ordischarge end thereof is always less than that maintained at the feedgate 8| and is dependent upon the position of the outlet gate 12 in thedischarge opening 20. Thus, a head of material is maintained between theinlet I9 and discharge opening 20 to effect movement of the material inthe desired direction. The chute 2| at its upper end also is as wide Aasthe hearth I8, that is, the distance between the hollow side walls 50.

The gas is supplied under pressure into the space 52 immediately beneaththe cells 41. The gas passes into the cells 41 through the pressurereducing gas apertures 49. The apertures 49 are of such size that thevelocity pressure of the gas entering the cells is substantiallyconverted to static pressure by the time the gas reaches the undersideof the perforated hearth I8. Stated another way, the jet effect of thegas produced at the apertures 49 is suiliciently dissipated in the upperparts of the cells 41, so that the gas will pass through the perforatedhearth I8 without subjecting the material therein to any pronouncedlocalized jet ell'ect.

As previously explained, the perforated hearth I8 is sieve-like incharacter and the gas passes therethrough with substantially noreduction in pressure. The distribution of the gas is more or lessuniform over the entire effective area of the hearth and flows throughthe interstices of the solids to aerate and effect bubbling thereof. Thegas is supplied to the underside of the hearth I8 at an adequate rate tomaintain the material in what may be referred to as a condition offluidity, in which condition the material isvagitated and bubblingthereof takes place and at the same time a general horizontal movementis imparted to the material which is in the direction toward the outlet20 due to the head of material between the inlet I9 and dischargeopening 28.

By providing a number of cells 41, the gas in space 52 in elect isbroken up into a number of streams each of which is effective to actupon a part of the bed of material.r In addition, the cells 41 andapertures 49 therefor are so proportioned and of such size that apressure reduction of the 9 latter without subjecting the material toany objectionable or undesirable localized iet eifect on account of thepressure velocity of the gas entering the cells.

In this way, uniform and steady ilow or movement of the material on thehearth I8 is promoted withoutl any `danger of clogging occurring orby-passing of gasthrough a void in the bed of material. Hence, allregions of the bed of material are more or less substantially in thesame fluid-like condition and the movement imparted to the material isgenerally uniform along all parts of the path of movement provided bythe hearth I 8 from the inlet I8 to the discharge opening 28, so thatpiling of the material at any particular region is avoided and thenormal average v depth of the bed of material is continuously maintainedat each particular region of the hearth.

An important advantage gained by use of apparatus like that shownandjust described is that the static pressure of the gas in anyparticular cell 41 will automatically vary independently of the staticpressure of the gas in the other cells,

when the average depth of the portion of thev bed of materialimmediately above it tends to int crease or decrease from its normalaverage depth.

When the average depth of a portion of the bed of material tends toincrease above its normal average depth, the static pressure in the cellor cells 41 immediately beneath such bed portion automatically increasesto overcome this condition. Conversely, when the average depth 'of aportion of the bed of material 'tends to decrease below its normalaverage depth, the static pressure in the cell or cells 41 immediatelybeneath such bed portion automatically decreases to overcome thiscondition.

'I'his automatic increase or decrease in static pressure of the gas inthe one or more cells 41 aifected is due, of course, to change inresistance to gas ilow resulting from the slight variation in averagedepth of the bed at a particular portion thereof. The static pressure inthe cells 41 can vary over a pressure range up to a maximum valuesubstantially corresponding to the static pressure of the gas in thespace 52 at the inlet side of the apertures 49. It is desirable toadjust the maximum depth at which the bed of material is maintained atthe inlet end I9 of the hearth I8 with respect to the maximum staticpressure that can be developed in the cells 41. By maintaining themaximum depth ofthe bed of material at the inlet end of the hearth suchthat it can be eectively uidized .and aerated when the static pressuredeveloped in the cells is somewhat less than the maximum value justreferred to, the bed of material throughout the length of the hearthwill always be maintained in'a condition of uidity and insure a generaluniform horizontal movement of the material to- Y ward the dischargeopening 2li.

Among the factors to be considered, in order to maintain an adequateiiow rate of gas through the bed of material 'and insure substantiallycomplete conversion of the velocity pressure of the gas to staticpressure, are the number and size of the apertures 49 and the height ofthe cells 41. In -the instant embodiment, a number of apertures 49 areprovided at the bottom of each cell 41 whose aggregate cross-sectionalarea is such that an adequate ow rate of the gas will be obtained.Further, the apertures 49 preferably are of such' size that gas issupplied to the underside of the bed of material on the l0 hearth I8 ina manner characterized by the absence of any objectionable jet effect atlocalized regions of the hearth.

When fewer gas apertures 48 are employed. experience has shown that theheight of the cells 41 must be increased. Whilev a single aperture 48 ofappropriate size may be employed for each cell 41, the height of thecells becomes unduly great. Hence, it is preferable to employ amultiplicity of apertures 48 of appropriate size and provide cells 41 ofsuiilcient height to accomplish the desired end result. e y

Additional factors to be considered to obtain the desired -ilow rate ofgas supplied to the underside of the hearth I8, for example, are thedensity of the material involved, the size of the particles of materialand the depth ofthe bed of material to be maintained on the hearth. Ineach instance, the parts of the apparatus of the invention can beproperly proportioned,'taking into consideration the above factors, tocause movement of material along the hearth in the manner justdescribed.

In the embodiment of the invention shown, the gases are immediatelywithdrawn from the hearth space 5I through the roof portions 36 and 81after passing through thebed of material on the hearth I8. When a gasrecirculation system is employed like that shown in Fig. 2, it isdesirable to maintain the pressure in the hearth space Il, immediatelyabove the bed of material, substantially at atmospheric pressure.

In order to reduce heat losses and avoid objectionable cooling of theparticles of material when such particles contact the side walls 50,such side walls are preferably hollow, as previously described. A partof the gas in the space 52 beneath the cells 41 is diverted and passesthrough the opening 56 into the hollow side walls 50. In passing throughthe hollow walls 50 the heated gases are subdivided into a plurality ofstreams in the vertical channels formed by the partitions 48 and walls55 of the refractory shapes.

At about the level of the hearth I8 the heated gases in the hollow sidewalls pass through the openings in the locating pins 6I into the hollowtubes 60. The heated gases in passing through the hollow tubes SII heatthe inner surfaces thereof and consequently reduce the temperaturedifferential at the inner and outer surfaces of the inside parts of thetubes which form the j inner refractory lining for the hearth space 5|.f In this way, the particles of material will not be initially heated bythe heating gases supplied to ,y the underside of the hearth I8 andsubsequently y come in contact with a cooler surface. In certaininstances, even the slight cooling of particles coming in contact withthe cooler side walls adversely affects the uniform heating of thematerial and results in a non-uniform end product. By maintaining theopposite surfaces of the inner refractory lining of the hearth space 5Iat approximately the same temperature, the particles of material movingalong the hearth I8 cannot come in contact with low temperature surfacestending to disturb the uniform heating of the particles of material.

By providing the thermocouple members 61 and 68 in the space 52 whichare operatively associated with the electromagnetically operable valves1| as shown in Fig. 6 and previously described, the temperature of thegas supplied maintain the gas at a desired elevated temperas-.saeeee iture Whentheg'esinspecettendstemcmse or decrease trcmitbe elevatedtempera l ture,y the electromamieticalhy operable valves respond toi theaction of the thermnccuple mem 3e te the burners Il?,

providing the thermccouple member 'is at the.I outletl lend or thehearth it which is operl l ath/'elyY associated: with the control systemm.

Fig.. 5a and` previously described. a, control; is; pro.- vided to,-insure that; the. about to;- leave the.: hearth le and pass into thedischarae open,- l ing 2li is always at; the same elevated temperature..When the temperature or the material y abouttopass into, theI dischargeopening; 2l tends to decrease and increase from the desired ele vatedtemperature, the discharge-geteilt responds.v to the action of thethermocouple member' 13 and; moves downwardly 'and upwardly,respectively, to vary the effective size of; the. discharge opening 2d,

When the outlet gate l2 moves downwardly,

the rate at which the material leaves the hearth.

I8 through the discharge opening 23". is reduced,

mocouple member '13. This reduces the head of 1 material maintainedbetween the inlet 191 and outlet 2li to reduce the rate at whichkmaterial; is-

conveyed on the hearth. Cox'alversely,r when. the

gate l2, moves upwardly, the rate at. which, the

This

The apparatus of the invention is suitable for i use with a variety ofmaterials or solids of relatively small size or in subdivided fornn As'prel vously stated, the gas employed to fluidize the material may simplyeiIect movement thereof without reacting physically or chemically withthe material- Howeventhefurnaceunitl'lillustrated in the drawings anddescribed above is particularly adapted for use with a heating gas lwhich reacts chemically and/or physically with the solids to eilcct thedesired treatment thereof while movement of the material isbeingpromuted by the gas.

By way of example and without limitation, the

furnace unit II may effectively be employed for roasting conce, cocoabeans, peanuts, cereals and l i similar products, to eect the reductionof metal- 1 lic ores, and for heating refractory balls or pebbles to anelevated temperature for immediateuseasacatalystinthecatalyticcrackingof j hydrocarbon oil.

The furnace Il! is particularly suited for heating subdivided materialwhich requires heating 'e in several heating stages. One example of vamaterial requiring heating in two heating steps is raw glass batch whichis in the form of rela.-

` tively small granules which contain considerable free and combinedwater. It is extremely desirable to remove both free and combined waterfrom raw glass batch granules because thepresence of water in themelting tank causes foaming and results in imperfections, such asbeading, for example, in the glass produced.

When the funace unit I0 is employed lor heat f ittrcatingwetravwglasshatclngranulemthewd granules are-delivered te theemr oli the hearth Itr roof-portion 3,51?, the higlr eases are employedte drive,- o free weten substantially all. ct` the. nee water isvaporized, the granules: move inta the secondi zone beneath. theroofportion 3i in which 1S effected, that; is combined water is;remcvedi from 1 the raw batch granules Since:

quzasntities of free water removed from. the granules in the; heatingzonen. gases. containing the moisture are; preferably diefcharged fromtheroof portion 3l the conduit 38; into the atmosphere., On the otherhand, the quantity of combined water, removed from the granules in thesecond heating zone, .is such that: in instances the spenti gases. canbe recirculated. in the manner: shown in FigcA 2;, In order toeiectively segregate the spent gases 'in the two heating zonesv theparti;-

tion 64 is; provided between the root portions 3G? and 3T.

The partitions 65 and 6l inthe heating space 51 and shell I( areprovided so. thatl gas; may be supplied at diilerent volumetric rates.to. the heating zones when this becomes necessary.. This is particularlytrue when the furnacey unit l 01's employed to heat treat raw glassbatch granules in which the rstheating zone requires heating. gas to besupplied thereto at a higher volume rate than inthe second heatingzone.. This is; so because the heated gas, which is supplied to thefirst heating zone to maintain. the wet granules in a condition ofuidity, isy contracted to such an extent that an excess or additionalquantity .of heated gas must be supplied to the underside of the hearthto maintain the granules in the desired condition of fluidity.y In otherWords,y heated gas at a. smaller volume rate is required in the secondheating zone beneath the roof porV` tion 36 to remove combined water andmaintain the granules therein in the same condition or fluidity as thewet granules containing free waterand in the rst heating zone beneaththe. roof portion 3l.

In such case, a separate blower may be connected to supply air to thepart of the shell M beneath the roof portion 3l and at one side of thepartition 6G. Likewise, since the volume rate at which heated gas issupplied to the heating zone beneath the roof portion 3l is greater thanthat at which the gas is supplied to the heating zone beneath the roofportion 3E, separate manifolds 3l and` 32 are provided for the burners25 in each of the zones and the supply of com.- bustible gas mixture isindependently controhcd for the two heating zones by the. thermocouplemembers 61 and 68 in the space 52 at opposite sides of the partition 65.

In view of the foregoing, it will now be: urider- A stood that I haveprovided an improved appch ratus for conveying solids of relativelysmall size or in subdivided form by maintaining the solids in a duidcondition with the -aid or a gas.

vidual solids or particles of material when this is desirableand-becomes necessary.-l f :[.thereforeintend in the followingtclaims.tol cover all modi-j iications .which do-not; depart fromthezrspiritland. scope of the. invention.

What isclaimed is: f 1 w 1 1. Apparatus for heating. subdividedy'material and the like comprising structure providing `an elongatedperforated hearth and; spaced apart hollow side ywalls at oppositesidesr thereof, and means for supplying heated gas to` said hollow sidewalls for flow therethrough and for supplying heated gas directly fromthe same source and at the same temperature to the underside of saidhearth for flow therethrough to effect heating of the material and atthe same time maintain the latter in a condition of fluidity to causeflow thereof along the hearth.

2. Apparatus for heating subdivided material and the like comprisingstructure providing an elongated perforated hearth and spaced aparthollow side walls at opposite sides thereof and including achamber'communicating with said side walls and the lower part of saidhearth, and means for supplying heated gas through said chamber to saidhollow side walls for vertical flow therethrough and for supplyingheated gas from the same source to the underside of the hearth for flowtherethrough to effect heating of the material and at the same timemaintain the latter in a condition of iiuidity to cause flow thereofalong the hearth.

3. Apparatus for heating subdivided material and the like comprisingstructure providing an elongated perforated hearth and spaced aparthollow side walls at opposite sides thereof, a plurality of burners andmeans for supplying heated gas directly from the burners to theunderside of the hearth for iiow therethrough to effect heating of thematerial and at the same time maintain the latter in a condition offluidity to cause flow thereof along the hearth, said means beingconnected with said side walls so that a portion of the heated gassupplied to the underside of said hearth is diverted and passes upwardlythrough the hollow side walls.

4. Apparatus to effect a change in temperature of subdivided materialand the like comprising a perforated hearth, means for supplying gas atadesired temperature to the underside of the hearth for flowtherethrough to effect a change in temperature of the material and atthe same time cause movement thereof along the hearth, and meansresponsive to a condition influenced by the temperature of the materialfor controlling the rate of movement thereof on the hearth.

5. Apparatus to effect a change in temperature of subdivided materialand the like comprising a perforated hearth, means for supplying a vgasat a. desired temperature to the underside of the hearth for flowtherethrough to eifect a change in temperature of the material and atthe same time cause movement thereof along the hearth, and meansincluding a thermal responsive element arranged to be contacted bymaterial on the hearth for controlling the r'ate of movement thereof onthe hearth.

6. Apparatus to eifect'a change in temperaturey sufficiently lowtemperature to freeze the indi-1 f time maintain the latter in acondition of fluidity to cause movement thereof, control means includingfa; `movable member at the discharge'end of-theihearthzfor controllingthe depth of the bed of material, and means responsive to a conditioninfluenced by the temperature of the material for regulating saidcontrol means.

' 7; Apparatus-to effect a change in temperature of subdivided materialand the like comprising a perforated hearth, structure to provide gas,control means to control the tempera.-l ture at which the gas isprovided by said structure, means to supply the gas to the underside ofthe hearth for flow therethrough to effect a change in temperature ofthe material and at the same time maintain the latter in a condition offluidity to cause movement thereof, means responsive to the temperatureof the gas supplied to the underside of the hearth for regulating saidcontrol means, and means responsive to a condition influenced by thetemperature of the material for controlling .the rate of movementthereof on the hearth.

8. Apparatus for heating solids of relatively small size or insubdivided form comprising means providing a perforated hearth, meansfor supplying gas at an elevated temperature to the underside of thehearth for ow therethrough to heat the solids and at the same timeeffect bubbling thereof to cause movement of the solids along thehearth, and means responsive to the temperature ofthe solids about topass from the hearth at the discharge end thereof for controlling therate at which the solids are discharged from the hearth.

9. Apparatus for heating solids of relatively small size or insubdivided form comprising structure providing a refractory linedchamber, means including screening of high temperature alloy materialproviding an elongated hearth disposed between theopposing side walls ofsaid chamber, means including spaced partitions providing a series ofcells at the underside of said hearth in unobstructed communicationtherewith, said partitions being disposed transversely of the elongatedhearth and extending between said opposing, side walls, said cells atthe bottoms thereof having pressure reducing gas aperturesextendingtherethrough, said structure also providing an 'unobstructedrefractory lined space beneath said cells extending the length of saidhearth, and means including burners for producing gas at an elevatedtemperature and supplying such gas to said space. l

10. Apparatus as set forth in claim 9 in which said opposing sidewallsiare hollow and a part of the gas supplied to said space passesthrough said side walls.

11. Apparatusas set forth in claim 9 in which said burners are embodiedin said structure at a refractory lined region thereof communicatingwith said space, and means for recirculating gas from the space abovesaid hearth to said region.

12. Apparatus as set forth in claim 9 in which said burners are embodiedin said structure at a refractory lined region thereof communicatingwith said space, and structure including 'conduit meansanda blowerconnected therein for recirculating gas from the space above said hearthtosaid region, said conduit means having damper controlled openings fordischarging spent gases and for introducing make-up air.

13. Apparatus to effect a substantial change in temperature of solids ofrelatively small size or in subdivided form comprising structure promaar`vidinganelongmteziperforatedhearthandspaced 'apart hollolsidewallsatoppositesides thereof, `mecenate supply gas to thermales-side of the`l'ielnrthforowtherethroughto:etl'ecttiiedcsireci change in temperatureo! thesolids and at the same time maintainthe ktterin s condition offluidity. te canse t valong the hearth; for supplying te the hollowrsidewallsforiiew therethrough a gas: im the same temperature range asthe `gaa supplied to the 1li. l`

undersideofthe same,- tinie maintain the latter im a condition. ofi 20AIuldity to. cause movement;- thereo along'. the

"hearth, means being' formed and arranged so thaty a;Y portion.y of thegas supplied. to" the und'ersicier of said hearth is; diverted` andpasses.A upwardly' through the'hollowrside walls.. 151 Apparatusforheating subdivided. material in combination anelongated. perforatedhearth, means` supporting salti. hearththroughout its lengthirxcluding;` structure forming a. plurality of individual.. cells, meansformingy a plurality oi passages extending. along; eachside ofsaidhearth,y structure located below said cells and". passages forming: acontinuous supply path leadingrto-eaclr cell and. passage, 'meanssimultaneously toforce airV through said. cells and. hearth, andthrough. said passages, and burner means located adjacent to supply pathto` introducehot products; ofcombustion. into said air. Y

16. In. apparatus for heatingl matey rial the combination of a. furnacehavingi an. elon.- 40% through. said openings. and

gated, chamber therein, the lower portion of said chamber beingconstricted to form.- a centrallyl disposed slot extending the length ofsaid chamber, means forming a plurality of psages. lining; the sides ofsaid chamber, an elongated perfo.` rated hearth upon which the materialto be heated is placed, means to mount said hearth in said chamber nearthe lower ends of said passages, and means to force air through saidslot and through said hearth and passages.

1 17. The combination of claim 16 including burner means locatedadjacent to and in communication 'with said slot whereby products ofcombustion may be discharged into the air ow'- ing through saidslot.

18. In apparatus for heating subdivided mate-Y rial the combination of afurnace having an elongated chamber therein, the lower portion of saidchamber being formed to provide an elongated air inlet, ilue means' atthe top of said chamber through which air may be withdrawn, an elongatedperforated hearth, means to mount said hearth in said chamber to dividethe same into an upper and a lower space, the material to be heatedresting on sm'd hearth in said upper space,

means forming a plurality of compartments in said lower 'spacethroughout the length of said hearth, each compartment being in opencoml 1e municetion with the lowery side of the hearththe lower. endsoiPv each compartment beine formed with pressure reducing openings,means to force air through said'inlet,` compartments and hearth to seidnue, and meansto heat'said air.

19.y The combination of' claim 18 in which the means to heat the aircomprises a plurality of burners located adjacent to said inlet and incommunication therewith, whereby products of combustina from the burnersheats the air forced through the inlet. 20. In apparatus to heatsubdivided material the combination of furnace structure forming anelongated chamber, the lower portion of saidv chamber being'.rconstricted to formV an elongated airinlet slot extending substantiallythe length oi said chamber, a. ilue at thetop` of said chamber, aperforated hearth, means to mount said hearth. in saidv chamber' to;divide the same into arr upper space into which. the material to beheatedi's placed' and. into a lower space, burners locatedv inv saidstructure adjacent.l to said'l slot and incommunication therewith todischarge products of combustionA into said? slot, land means to force,air through. said. slot into: said lower space,

l from. which. it: passes through. said. hearth and the materialthereonzto the flue..

2l. The combination oit claim 20 including means forming a plurality ofcompartments or cells. in said lowerv space, each. compartment being indirectcommunication with a portion of said hearthfand. eachcompartmentbeing: provided in its` lowerv end with pressure.- reducing. openingsthrough whichthe. air flows tothecompartments.

22; The combination of` claim 21 including means. forming' a plurality#of' passages in. said chamber on: each` side of' said. hearthv andextending above the same, said means: being provided withy openings at:thelowerendl-thereof communi-Y eating. withv said. lower.v space;whereby air will' flow passages: as: well as through said hearth..

23. The combination. of' claim 20 including means in said'. chamber.yformingy a.l plurality of passages'. on. each side. of said hearth andwhich` is contacted: by the. materialy on said hearth, said means beingprovided with. openings below the hearth. to; connect said passages andlowery space whereby the air may flow through said passages as well as:through said hearth.

JAMES B. HENWOOD.

REFERENCES CITED The following references are of record in the le of.this patent:

y UNITED STATES PATENTS Number OTHER REFERENCES Page 195, IndustrialFurnaces, v01. 1I, 2nd edition, by W. Trinks; copyright 1942, andpublished -by John Wiley & Sons, New York, N. Y.

